[te_platt]

Maybe. My guess is there is a correlation between {income and emphasis on education} and {emphasis on education and SAT scores}. It looks like you are saying at some score the SAT becomes something of an IQ test and IQs are more evenly distributed. I'm not sure that is the case.

[parse_tree]

No. I think SAT score would be correlated with IQ, but not too strongly on its own (many not particularly brilliant people get high scores by preparing excessively). I think measured IQ and family income would, together, be quite good predictors of SAT performance. But what leads me to believe that also leads me to believe that predictive strength would tail off as family income (or IQ) got extremely high. E.g., for very smart people, the SAT is probably not a challenge, so their score wouldn't benefit much from 10 more IQ points. Similarly, very rich people can't use their money to do much for their kids SAT score than those making $150k / year can.

[Retric]

I think people that make a lot of money tell their children to focus on the important aspects of education. And prepping for the SAT has a much better payoff than most extracurricular activities.